The mechanical fragility and small size of light-transmitting optical fibers have led to the development of the optical fiber ribbon structure. Such a structure typically comprises a plurality of nominally spaced, coplanar and parallel optical fibers embedded in some supporting medium. The medium mechanically protects the fibers while the fiber spacing geometry facilitates gang splicing.
Prior art connectors, such as disclosed in U.S. patent application, Ser. No. 724,653, filed Sept. 20, 1976, and assigned to the assignee hereof, featuring fiber-receiving grooves have been found to facilitate accurate and reliable low-loss splices between ribbons of fibers. These prior art connectors rely on the precise fiber spacing geometry to place the fibers into the fiber-receiving grooves. When using these connectors, the supporting medium is stripped from the ribbon ends to expose the fibers for placement in the grooves, which have a spacing geometry corresponding to the nominal spacing of the fibers. In practice, however, after stripping, the fibers tend to wander and stray from their nominal spacing. Also, the fibers may deform and gain in misalignment from the stripping operation.
Sometimes the fibers are coated with additional protective layers before being embedded in a supporting medium to form an optical fiber ribbon. In such a ribbon, the fiber spacing geometry is generally made from the coated fibers. Because the protective layers often coat the fibers unevenly, the fibers are misaligned though the fiber spacing geometry is maintained. Thus, the coatings, along with the supporting medium, are removed to prepare the optical fibers for splicing.
Deviations from the nominal fiber spacing geometry make fiber insertion into the grooves of these connectors exceedingly difficult for the craftsman, especially in the outside plant. Additional steps are often needed to facilitate fiber placement. For example, one technique which can be used is precisely prealigning the exposed fibers in preliminary external fiber-aligning equipment and maintaining the prealignment while the fibers are placed into the grooves and until the splice is completed.
The additional steps complicate the splicing process and impose greater skill and dexterity on the craftsman in assembling a splice connection. Greater manufacturing restraints in fabricating splicing apparatus are also required to ensure alignment between the external fiber-aligning equipment and the connectors.
Also, this technique requires stripping of additional supporting medium away from the ribbon ends to permit prealignment in the external fiber-aligning equipment. Additional stripping results in less mechanical support and protection of the fibers desirable once the splice has been completed by leaving the fibers exposed where the external equipment held them aligned. This complicates ribbon termination in connecting hardware, which is desirable to mechanically protect the fibers and to facilitate use of the ribbon structure to strain relieve the splice joint.
One approach not using external fiber-aligning equipment requires that the fibers be in a touching array for placement in the grooves; the fibers support one another to maintain the desired spacing geometry. However, errors arise because if one fiber is offset, the offset is passed to the other fibers. Also, if one fiber breaks, the fiber spacing geometry is lost. Furthermore, this approach is not available where the fibers are coated and the protective layers must be removed for splicing.
Hence, it is desirable to develop connecting apparatus which relaxes the spacing requirements of the fibers.
It is also desirable that the connector include internal means for easing fiber insertion and holding the fibers in their respective grooves, thereby eliminating the need for external precision fiber-aligning equipment.
It is further desirable that the fibers be held in the grooves at the splice point during splicing.
Moreover, it is desirable that the splice connection be easy to assemble requiring a minimum of skill and dexterity on the part of a craftsman to effect a reliable low-loss splice joint.